The aim of the proposed work is to establish if any of the schistosome eggs passed by patients after therapy with schistosomicides are produced by drug-resistant worms and thus whether drug resistance could become a significant problem in schistosomiasis in Kenya and Africa. Schistosoma mansoni and S. haematobium eggs will be provided by patients who are incompletely cured while receiving therapy in clinic or hospitals in 3 areas of Kenya (Coastal Province for S. haematobium, Mwea District for S. mansoni, and Nairobi). Eggs will be used to infect Biomphalaria pfeifferi or Bulinus sp. of snails and mice (S. mansoni) or hamsters (S. haematobium) will be infected with the resultant cercariae. Mature S. mansoni infections in mice will be dosed with hycanthone or oxamniquine or praziquantel and mature S. haematobium infections in hamsters with metrifonate or praziquantel. From the efficacy of the treatment in rodents it will be known what percentage of incomplete cures in patients are due to drug-resistant schistosomes, and whether there is a direct correlation between percentage cure and drug resistance, which would permit rapid surveys for resistance in the field. Since, however, there may be no correlation and infection and dosing of rodents is time consuming and expensive, simpler tests for detection of drug resistance in schistosomes, which are currently under investigation, will be evaluated as relevant. The response to other schistosomicides of any drug-resistant strains that are isolated in the present study will be determined to provide a logical basis for clinical therapy. To reduce the cost and labor of maintaining schistosome isolates that might be derived from the present study, an attempt will be made to cryopreserve schistosome sporocysts which could then be used to infect further snails by microsurgical transplantation. Cryopreserved cloned sporocysts of drug-resistant schistosomes would be an advantage for future research into drug resistance mechanisms, genetics of drug resistance and evaluation of novel chemicals for potential cross resistance.